Rotor End Ring Casting Oxide Removal
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Solution Overview
Problem
The interfacial bonding between cast end rings and pre-formed conductor bars in rotor assemblies for electric devices is compromised by aluminum oxides, leading to reduced bond quality and integrity.
Innovation Solution
A method involving the injection of liquid aluminum at high temperatures into a mold around the conductor bars, circulating it to heat and fracture oxide films, and then flushing away the oxides to create a strong bond between the aluminum and the conductor bars, ensuring a high-quality bond formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid aluminum is cast in place over pre-formed conductor bars, then the end rings are formed and electrically connect the conductor bars, but aluminum oxides on the conductor bars prevent and/or reduce the quality of the bond between the end rings and conductor bars
Solution Approach 1:
The patent applies preliminary action by heating the conductor bars to 350°C or higher before casting the liquid aluminum end rings. This pre-heating treatment fractures oxide films on the conductor bar surfaces and reduces bond strength between oxides and the base metal, creating optimal bonding conditions before the aluminum is cast. The process also includes flushing oxides away with circulating liquid aluminum before the final bonding occurs.
Solution Approach 2:
The patent changes physical parameters by heating the conductor bars to elevated temperatures (350°C or higher) and controlling the temperature of the liquid aluminum during casting. These parameter changes facilitate oxide film fracture and improve the wetting and bonding characteristics between the liquid aluminum and conductor bars, resolving the oxide interference problem.
2Manufacturing precision
If the conductor bars are heated to high temperature to fracture oxide films, then oxide removal is improved, but energy consumption increases
Solution Approach 1:
The patent merges the heating function with the casting process itself. The liquid aluminum serves dual purposes: it acts as the bonding material for forming end rings and simultaneously serves as the heating medium to fracture oxide films and flush oxides away. This combination eliminates the need for separate heating equipment and reduces overall energy consumption while achieving high-quality oxide removal.
Solution Approach 2:
The liquid aluminum performs self-service by using its own thermal energy to heat and treat the conductor bar surfaces. As the liquid aluminum circulates during the casting process, it naturally transfers heat to the conductor bars, fracturing oxide films without requiring external heating sources. The aluminum essentially prepares its own bonding surface through its inherent thermal properties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively reduces the bond strength between oxides and conductor bars, allowing for the removal of oxides and subsequent formation of a high-quality bond between the aluminum and conductor bars, enhancing the integrity of the rotor assembly.
Implementation Method 1
The liquid aluminum is circulated within the first cavity and around the first ends of the conductor bars. Circulating the liquid aluminum heats the conductor bars to a temperature equal to or greater than approximately three hundred fifty degrees Celsius (350° C.), which reduces a bond strength between the conductor bars and any oxides formed on an outer surface of the conductor bars, and fractures any oxide films on the outer surface of the conductor bars.
Implementation Method 2
The liquid aluminum is circulated at a speed sufficient to create a drag force on the oxides disposed on the outer surface of the conductor bars that is greater than the bond strength between the oxides and the conductor bars.
Implementation Method 3
cooling the liquid aluminum within the mold to form a first end ring over the first ends of the conductor bars
Data Source
AI summary
A method of manufacturing a rotor assembly includes positioning a laminated stack of electric steel sheets with a plurality of conductor bars positioned within longitudinal grooves defined by the laminated stack in a mold, and casting an end ring in place over ends of the conductor bars. In order to cast the end ring in place, heated liquid aluminum is injected into a cavity defining the end ring, and circulated within the cavity and around the ends of the conductor bars to create relative movement between the liquid aluminum and the ends of the conductor bars to heat the conductor bars and flush oxides away from an outer surface of the conductor bars.